Microsoft to patch Home Server corruption bug -- in June

Microsoft Monday said its engineers were still "heads down working" on the data corruption bug that has plagued Windows Home Server since late last year, but acknowledged that a fix wouldn't be released until June at the earliest.

In a post to a company blog, the Windows Home Server (WHS) team said it had updated a support document to provide more information on the flaw -- even as it continued to downplay the threat. "We are aware of only a very small percentage of users with confirmed instances of this issue, and we believe that most people are unlikely to be affected," the team said.

The WHS developers, who also said that some claims of corrupted files had been traced to other causes, spelled out a rough timeline for a patch. "Our current plan is to release beta test versions of a fix over the next few months, with a final version currently estimated for June 2008, although that date could change as testing progresses," the programmers said.

Before Monday's update, the last time the WHS group had refreshed the support document outlining the flaw was nearly three weeks ago, when it expanded the list of programs that could damage data.

WHS's data corruption problems go back to December 2007, when Microsoft confirmed that editing a document, image or e-mail stored on the server could corrupt the file, effectively destroying the data. Since then, WHS product managers have struggled to pin down the bug, saying in December that it cropped up only when the server was under an "extreme load" as it copied large files. They recanted that explanation just weeks later.

According to Monday's post, however, the team now knows what's going on. "We understand the issue really well at this point -- it is at an extremely low level of the operating system and it requires thorough testing to ensure that the fix addresses the issue."

In the revised support document, Microsoft went into greater detail about the cause of the data corruption flaw. "A bug has been discovered in the way that Windows Home Server manages file transfer and balancing across multiple hard drives," said the document. "In certain cases, depending on application use patterns, timing, and the workload that is placed on the Windows Home Server-based computer, certain files may become corrupted."

The bug is in the redirection mechanism that WHS uses when writing data to more than one disk drive. By Microsoft's analysis, that can cause the Windows file system, as well as its Memory Manager and Cache Manager, to get out of sync, which in turn results in corrupted data being written to files.

The support document also included more specific advice for WHS users. "Do not use applications to directly edit or change files that are stored on the Windows Home Server-based computer," Microsoft recommended. "As a precautionary measure, users should use Windows Explorer or a command-line tool to copy files to and from the Windows Home Server-based computer."

Other tips included setting the Shared Folders on a WHS machine to "read-only"; not using media software such as Windows Media Player to import files to the server; and avoiding redirecting applications to access files stored in Shared Folders.

"Developing a fix for this issue is the highest priority for the team right now," said a company spokesman in an e-mail Monday.